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21.
We examine the sequence of changes in the structure of the geosystems of the Primorsky Range (Baikal region) for the last 6000 years, based on a continuous recording of fluctuations of the vegetation reconstructed from spore-pollen complexes of a high peat bog. We determined the chronological timeframe of paleogeographical events. The study showed that there occurred a radical structure transformation of the geosystems in the mid-late Holocene, along with a recurrence of similar landscape transformations caused by the instability of natural conditions. 相似文献
22.
M. A. Krainov E. V. Bezrukova A. A. Shchetnikov E. V. Kerber 《Doklady Earth Sciences》2018,481(2):980-983
The first results of radiocarbon dating of the Gothenburg and Mono Lake paleomagnetic excursions identified in a sedimentary section of bottom sediments of Baunt Lake (Northern Transbaikalia) are presented. The exact geochronological positions of these excursions are 13.2 and 25.8 ka, respectively. The estimated time of existence of the paleomagnetic events of ~100 and 500 years for the Gothenburg and Mono Lake excursions, respectively, can serve as geochronological markers for understanding the real time over which such global changes in the Earth’s magnetic field can occur. 相似文献
23.
E. N. Tarasova E. V. Bezrukova E. A. Mamontova A. A. Mamontov M. I. Kuzmin 《Doklady Earth Sciences》2016,470(1):946-949
Based on measurements of the concentrations of C, N, P, and chlorophyll-a, as well as on palynological analysis of the core Vdr 2011 of peaty sediments from the Vydrinaya River along the southern coast of Lake Baikal, the geochemical characteristics of eutrophy were compared to pollen indices of changes in the environment and the mode of marsh ecosystem transformations into various trophic states was specified. It was shown that geochemical parameters of the changes in the environment may be considered as the characteristics of trophic conditions in ecosystems in the course of paleo-reconstructions. 相似文献
24.
Quantitative reconstruction of the last interglacial vegetation and climate based on the pollen record from Lake Baikal, Russia 总被引:1,自引:0,他引:1
P. Tarasov W. Granoszewski E. Bezrukova S. Brewer M. Nita A. Abzaeva H. Oberhänsli 《Climate Dynamics》2005,25(6):625-637
Changes in mean temperature of the coldest (T
c) and warmest month (T
w), annual precipitation (P
ann) and moisture index (α) were reconstructed from a continuous pollen record from Lake Baikal, Russia. The pollen sequence
CON01-603-2 (53°57′N, 108°54′E) was recovered from a 386 m water depth in the Continent Ridge and dated to ca. 130–114.8 ky
BP. This time interval covers the complete last interglacial (LI), corresponding to MIS 5e. Results of pollen analysis and
pollen-based quantitative biome reconstruction show pronounced changes in the regional vegetation throughout the record. Shrubby
tundra covered the area at the beginning of MIS 5e (ca. 130–128 ky), consistent with the end of the Middle Pleistocene glaciation.
The late glacial climate was characterised by low winter and summer temperatures (T
c ~ −38 to −35°C and T
w~11–13°C) and low annual precipitation (P
ann~300 mm). However, the wide spread of tundra vegetation suggests rather moist environments associated with low temperatures
and evaporation (reconstructed α~1). Tundra was replaced by boreal conifer forest (taiga) by ca. 128 ky BP, suggesting a transition
to the interglacial. Taiga-dominant phase lasted until ca. 117.4 ky BP, e.g. about 10 ky. The most favourable climate conditions
occurred during the first half of the LI. P
ann reached 500 mm soon after 128 ky BP. However, temperature changed more gradually. Maximum values of T
c ~ −20°C and T
w~16–17°C are reconstructed from about 126 ky BP. Conditions became gradually colder after ca. 121 ky BP. T
c dropped to ~ −27°C and T
w to ~15°C by 119.5 ky BP. The reconstructed increase in continentality was accompanied by a decrease in P
ann to ~400–420 mm. However, the climate was still humid enough (α~0.9) to support growth of boreal evergreen conifers. A sharp
turn towards a dry climate is reconstructed after ca. 118 ky BP, causing retreat of forest and spread of cool grass-shrub
communities. Cool steppe dominated the vegetation in the area between ca. 117.5 ky and 114.8 ky BP, suggesting the end of
the interglacial and transition to the last glacial (MIS 5d). Shift to the new glaciation was characterised by cool and very
dry conditions with T
c ~ −28 to −30°C, T
w~14–15°C, P
ann~250 mm and α~0.5. 相似文献
25.
The results obtained in Russian studies on clouds and precipitation in 2011–2014 are presented. These results are part of the Russian National Report on Meteorology and Atmospheric Sciences that was prepared for the XXVI General Assembly of the International Union of Geodesy and Geophysics (IUGG). 相似文献